Wenvoe Quarry (ST 131
741)
There has been a Significant Height Revision to a
hill that is listed in the 100m Twmpau and
Y Trechol – The Dominant Hills of Wales,
with the summit height and its position confirmed by LIDAR analysis conducted
by Myrddyn Phillips.
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| LIDAR summit image of Wenvoe Quarry (ST 131 741) |
The criteria for the two listings that this height
revision applies to are:
100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m
minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all
Welsh hills at or above 100m and below 200m in height with 20m or more and
below 30m of drop, with the word Twmpau
being an acronym standing for thirty
welsh metre prominences and upward.
Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose
prominence equal or exceed half that of their absolute height. With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose
prominence is between one third and half that of their absolute height. The list is authored by Myrddyn Phillips with
the Introduction to the start of the Mapping Mountains publication of this list
appearing on the 3rd December 2015.
The name the hill is now listed by is Wenvoe
Quarry and it is adjoined to the Bro Morgannwg group of hills, which are
situated in the southern part of South Wales (Region C, Sub-Region C2), and it
is positioned with a number of A roads encircling it with the A4232 to its
north and east, the A4050 to its west and the A4055 further to its south-east, and
has the city of Caerdydd (Cardiff) towards the north-east.
When the original Welsh 100m P30 list was
published on Geoff Crowder’s v-g.me website this hill was listed with a c 115m summit
height, based on the uppermost contour on contemporary Ordnance Survey 1:25,000
Explorer maps.
When this list was standardised, and interpolated
heights and drop values also included the details for this hill were
re-evaluated and it was listed with an estimated c 117m summit height based on
interpolation of the uppermost 115m contour on the Ordnance Survey 1:25,000
Explorer map, with this summit height later being changed to an estimated c
118m.
 |
| Extract from the Ordnance Survey 1:25,000 Explorer map |
However, it was not until LIDAR became available
that the details for this hill could be accurately re-assessed. The LIDAR (Light Detection & Ranging)
technique produced highly accurate height data that is now freely available for
much of England and Wales.
The height produced by LIDAR analysis is 123.4m and
is positioned at ST 13189 74189, this is
a substantial revision compared to some revised heights, and comes within the
parameters of the Significant Height Revisions used within this page heading,
these parameters are:
The term Significant Height Revisions applies to
any listed hill whose interpolated height and Ordnance Survey or Harvey map
summit spot height has a 2m or more discrepancy when compared to the survey
result produced by the Trimble GeoXH 6000 or analysis of data produced via
LIDAR, also included are hills whose summit map data is missing an uppermost
ring contour when compared to the data produced by the Trimble or by LIDAR
analysis.
Therefore, this hill’s new listed summit height is
123.4m and this was derived from LIDAR analysis, this is 5.4m higher than the
previously listed summit height of c 118m which was based on an estimated
height from interpolation of its uppermost 115m contour on the Ordnance Survey
1:25,000 Explorer map.
The full details for the hill are:
Group: Bro Morgannwg
Name: Wenvoe Quarry
OS 1:50,000 map: 171
Summit Height (New Height):
123.4m (LIDAR)
Summit Grid Reference:
ST 13189 74189 (LIDAR)
Bwlch Height: 66m
(spot height)
Bwlch Grid Reference:
ST 12669 74393 (spot height)
Drop: 57m (LIDAR
summit and spot height bwlch)
Dominance: 46.51% (LIDAR
summit and spot height bwlch)
Myrddyn Phillips (October 2019)
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